FI96767C - Process for the preparation of the trisodium salt of isoserine N, N-diacetic acid - Google Patents

Description

96767

Process for the preparation of the trisodium salt of isoserine N, N-diacetic acid

The present invention relates to an improved process for the preparation of the trisodium salt of isoserine N, N-diacetic acid of formula I:

NaOOC-CH, OH

\ I

N-CH 2 -CH-COONa (I) 10 NaOOC-CH 2 by reacting acrylonitrile with aqueous hydrogen peroxide to give the glycidic acid amide of formula II: 15.0. H2C-CH-C-NH2 (II) followed by further reaction of compound II with the disodium salt of iminodiacetic acid of formula III:

NaOOC-CH-, NH (III)

NaOOC-CH 2 Cl 2 and the solution thus obtained are reacted with a basic sodium compound to give a compound of formula I.

::: The older DE patent publication P 37 12 330 (1) 30 describes a process for the preparation of the trisodium salt I which is suitable for use as a complexing agent, kan-,. as an agent and a bleach stabilizer in detergents and cleaners, wherein according to the method glycidic acid amide (II) is added to an aqueous solution of iminodiacetic acid in the presence of twice the molar amount of sodium hydroxide, followed by hydrolysis of the amide group in sodium hydroxide solution.

Compound II is prepared according to DE-A 19 04 077 (2) by reacting acrylonitrile with an aqueous solution of hydrogen peroxide in a narrow pH range, for example at pH 7.2 to 7.4. The unreacted acrylonitrile is then removed by distillation and the excess peroxide is destroyed using a catalytic amount of a manganese compound.

10 The synthetic methods presented in sources (1) and (2) are discontinuous in nature. The disadvantages of these methods are that the heat removal is difficult to control, especially when acrylonitrile reacts with hydrogen peroxide to give compound II, and that the pH is kept constant. In addition, in accordance with the procedure described in (2), a significant yield loss due to the thermal loading of compound II may occur during the distillation of unreacted acrylonitrile and the subsequent destruction of the excess peroxide by the manganese compound.

The object of the invention was thus to provide an implementation technique for a process for the preparation of compound I which would certainly be controllable in its reactions and which would give relatively high yields (in terms of time and reaction volume).

Accordingly, a process for the preparation of trisodium salt I was obtained by reacting acrylonitrile with an aqueous solution of hydrogen peroxide to give glycidic acid: / · 'amide (II) and then reacting compound II II with disodium salt III and reacting the solution thus obtained. a basic sodium compound. . *. to obtain a compound of formula I, the process being characterized in that it is carried out in a continuous manner, the following steps being carried out in succession: 3 96767 a) acrylonitrile and aqueous hydrogen peroxide are reacted at pH 7-8 and at a temperature of 30 ° to 60 ° C, b) the unreacted acrylonitrile is removed by distillation, c) the reaction mixture is passed through a solid contact material to destroy hydrogen peroxide, d) the aqueous solution of compound II thus obtained is reacted with compound III at pH 7-9 and at a temperature of 40-90 ° C. eC, e) the solution obtained is reacted with a basic sodium compound at a pH of 9 to 14 and a temperature of 60 ° to 95 ° C, f) the ammonia formed is removed by distillation, and g) the aqueous solution of compound I thus obtained is further worked up in a manner known per se to give solid compound I .

Reaction steps a), 20 d) and e) of the process according to the invention are preferably carried out using a series of stirrers, at least two stirrers being required for each of these three steps (example: see the figure below). However, embodiments are also possible in which the agitator units of the plant have been partially or completely replaced by tubular reactors.

For successive separate steps *: *: a) to g) the following recommendations apply: • S * a) Acrylonitrile and aqueous hydrogen peroxide, • · · · containing 3 to 50% by weight, preferably 10 to 35% by weight , is reacted in a molar ratio of 1: 0.6 to 1: 1.5, preferably 1: 1 to 1: 1.2, of reactants in a mixer at a pH of 7-8, preferably 7.3 to 7.7, and warm- !! '. temperature 30 ° to 60 ° C, preferably 45 ° to 55 ° C. The average residence time in the mixer is usually 30 to 45 minutes. To keep the pH and temperature constant is added

• I

«4 96767 suitably in a dosage of from 5 to 50% by weight, preferably from 10 to 20% by weight, of sodium hydroxide solution. In one to three, preferably one, post-mixers, the reaction solution is post-mixed for pH and temperature under the same conditions as in the first mixer.

The average residence time in the latter mixer is usually 15 to 25 minutes.

b) The unreacted acrylonitrile in step a), usually in an amount of 10 to 30-10% by weight, is separated on a distillation column, which preferably operates on the principle of a thin-layer evaporator. The distillation column is preferably used at the temperature used in step a) and at a pressure of, for example, 120 to 160 millibars. Distillation with acrylonitrile usually removes a small amount of water. After distillation, the residual concentration of acrylonitrile in the reaction solution is usually 0.1 to 0.5% by weight. The separated acrylonitrile can preferably be taken back to step a).

c) To further decompose the hydrogen peroxide present, the reaction solution is passed through a solid contact material, which is preferably activated carbon. However, other solid materials can also be used to destroy the hydrogen peroxide, for example zeolite or non-water-soluble manganese, lead or vanadium compounds. The order of steps ·. · * 25 b) and c) can be changed, in which case, however, it is preferable first to distill the unreacted ac - *: **: alkyl nitrile.

··· (d) The resulting aqueous solution of glycidic acid amide (II), usually 15% by weight, is reacted with the disodium salt of iminodine-30 acetic acid (III) in an aqueous solution of the latter, usually 20 to 30% by weight, when. the molar ratio of reactants is 1: 0.9 to 1: 1.1, preferably • «· ;;; 1: 1, in a mixer at a temperature of 40 ° to 90 ° C, preferably 55 ° to 80 ° C. The post-stirring of the reaction solution is carried out in one to three, preferably two, post-stirrers. In this case, a temperature gradient can advantageously be used, the temperature in the last stirrer of step d) being 10 to 25 ° C, preferably 15 to 20 ° C, higher. The heat-5 space range assigned to the first mixer in step d) is valid for all mixers, including the last. In all the stirrers of step d), the pH of the reaction solution is 7 to 9, preferably 7.5 to 8.5. The average residence time in the first mixer is usually 15 to 30 minutes, which usually increases to 10 45 to 90 minutes in the last mixer.

e) The resulting aqueous solution of the disodium salt of 2-hydroxy-3-aminopropionic acid amide-N, N-diacetic acid is saponified to give the final compound I using 20 to 50% by weight, preferably 40 to 50% by weight, of a basic sodium compound. , for example an aqueous solution of sodium carbonate, or preferably sodium hydroxide, in a molar ratio of reactants of 1: 1 to 1: 1.7, preferably 1: 1.3 to 1: 1.4, in a stirrer at a temperature of 60 ° to 95 ° C, preferably 70 ° -85 ° C, and at a pH of 9 to 14, preferably 11 to 12.5. The post-mixing in one to three, preferably one, post-mixers uses the same conditions in terms of temperature and pH as in the first mixer of step e). In this case, a pressure gradient can advantageously be used, the last stirrer of step e) having a pressure of 200 to 500 millibars, preferably 250 to 400 millibars, lower than that of the first stirrer used at normal atmospheric pressure. In all sub-steps of step e), the average residence time is usually 50 to 100 minutes per sub-step. Most of the ammonia formed in the saponification is removed directly from »» step e) as a gaseous substance.

, f) The remainder of the ammonia formed in step e) is separated off as an aqueous mixture in a "Strip" or distillation column, which preferably operates on the principle of a thin-layer evaporator. The distillation column preferably uses the same temperature

«I

6 96767 spaces as in step e) and a pressure of 200 to 700 millibars, preferably 400 to 600 millibars. The remaining aqueous solution of the tri-sodium salt I is generally 10 to 20% by weight, the total solids content of which is usually 20 to 40% by weight and the pH is normally 11.5 to 13.

g) The aqueous solution of compound I thus obtained can be further worked up in a manner known per se, for example by spray-drying or freeze-drying, crystallization, mixing or evaporation to give solid compound I.

The advantage of the method according to the invention is based on the combination of several individual advantages, whereby the combined effect leads to an excellent overall result. Since acrylonitrile and hydrogen peroxide are suitably added in step a) with continuous dosing, whereby the reaction proceeds smoothly, dissipation of the heat of reaction released in the highly exothermic reaction does not present any difficulty. In this case, in step a), the pH-dependent pH value can be easily maintained at its narrow limit setpoint. The preparation of glycidic acid amide (II) 20 thus proceeds in a substantially more reproducible manner than when carried out according to the discontinuous method described in source (2).

The unreacted acrylonitrile is removed in the distillation of step b), preferably using a thin layer evaporator. 25 tens, almost perfectly. Get rid of distilled acrylonitrile • ·. Thanks to the possibility of recycling in the production process, the yield of compound II can be substantially increased.

By further destroying the hydrogen peroxide present, the conditions for oxidation and / or hydrolysis side reactions in the further steps of the process according to the invention are removed. In addition, the complete removal of hydrogen peroxide residues and any hydroperoxides present is also of safety significance due to their risk of explosion.

i *

• I

7 96767

Since the aqueous solution of compound II does not withstand storage, but decomposes rapidly, especially in the presence of heat load, the mild distillation and hydrogen peroxide destruction steps performed in steps b) and c) are crucial for the purity and concentration of the solution used in step d). An essential advantage of the process according to the invention is that the continuous implementation of solution II makes it possible to react immediately, as this largely avoids the decomposition reactions of compound II, which would lead to undesired by-products and cause yield losses of the final product compound I.

Since in step d), when reacting compound II with compound III, and in step e), when carrying out carboxylic acid amide saponification, a continuous procedure is used, the reactions take place more completely and, above all, are easier to control. The removal of residual ammonia formed in step e) in step f), preferably using a thin layer evaporator, represents a mild and efficient separation method in a manner similar to step b).

With regard to the total conversion of acrylonitrile to the final product compound I, it should be noted that this is a process with a high relative yield (in terms of time and V:25 reaction volume).

Example ·; ··: The purpose of the following example is to further illustrate the method according to the invention by means of the experimental apparatus schematically shown in the accompanying figure: V, 30 a) Dosing to the mixer R1 (volume 1.0 liters)? 255 g (4.8 mol) of acrylic were added at 50 ° C per hour. nitrile (AN) and 1200 g of a 15% by weight aqueous solution of hydrogen peroxide (equivalent to 5.3 moles of hydrogen peroxide), as well as 110 g of 10% by weight of sodium hydroxide per hour; 35 dilute solution (amount corresponding to 0.28 moles of sodium hydroxide) * * «I I * '•» • · · I I I I t »f 1 8 96767 so that the pH remained at 7.4 to 7.5. After a residence time of 38 minutes, the reaction mixture was transferred to stirrer R2 (volume 0.5 liters), where 60 g of a 10% strength by weight sodium hydroxide solution (corresponding to 0.15 mol of sodium hydroxide) were further added to keep the said pH constant. per hour. The temperature in mixer R2 was 50 ° C and the residence time was 18 minutes.

b) 58 g (1.1 mol) of unreacted acrylonitrile and 35 g of water per hour were removed from the reaction mixture in a Sambay thin-layer evaporator D1 with an operating temperature of 50 eC and an operating pressure of 140 mbar. The distillate was liquefied in a condenser K, after which phase separation in a separatory funnel S gave 55 g of acrylonitrile (AN) per hour, which was recycled to step a). The mixture obtained from the separating funnel S as the aqueous phase, containing 92% by weight of water and 8% by weight of acrylonitrile (AN), was used in step a) to prepare the required 10% by weight sodium hydroxide solution.

c) The reaction mixture was passed through a contact material unit Z comprising activated carbon in the form of granules 20 to destroy the hydrogen peroxide still present and any hydroperoxide trace concentrations. The amount of activated carbon was 150 g with an estimated free surface area of 500 m2. Thus, 1550 g per hour of an aqueous solution of glycidic acid amide having a concentration of 19% by weight (corresponding to a yield of 90%) and a residual acrylonitrile content of 0.1% by weight was obtained. % in the absence of analytically detectable amounts of hydrogen peroxide and / or other peroxides.

4. · *. * · '· D) The glycidic acid amide solution (II) obtained was stirred for 30 hours in 2360 g of a 25% by weight solution of the disodium salt of iminodiacetic acid (III) (equivalent to 3.33 mol of anhydrous reagent) at 55 ° C in a stirrer. R3 (volume 1.0 liters). After a residence time of 20 minutes, the reaction solution was transferred to a stirrer R4 (volume 2.0 liters) where it was 1 ': 35 at 65 ° C for 40 minutes. The solution then shifted to a ».

«I

a · i «« Iti «« I · «1 'I. I »* il 9 96767 to a stirrer R5 (volume 3.0 liters), the internal temperature of which was adjusted to 75 ° C and in which the solution remained for 60 minutes. The pH in the mixer R5 was 7.8 to 8.2.

e) The reaction solution was saponified to the final product in a mixer R6 (volume 4.0 liters) using 346 g of 50% strength by weight sodium hydroxide solution (equivalent to 4.33 moles of sodium hydroxide) per hour at a temperature of 80 eC and a pH of 11.8 to 12. 5. After a residence time of 80 minutes, the reaction solution was transferred to a stirrer R7 (volume 4.0 liters), where it was post-stirred at the same temperature, the same pH and the same residence time as the stirrer R6 at a reduced pressure of 700 mbar. Most of the ammonia formed in the saponification was discharged directly in gaseous form from the mixers R6 and R7.

15 f) To remove residual ammonia by distillation, 500 g of an ammonia / water mixture with a weight ratio of 1:70 were separated on a Sambay thin-layer evaporator D2 at a temperature of 80 ° C and a pressure of 500 mbar. The final product obtained was 3750 g per hour of an aqueous solution of the trisodium salt (I) of isoserine-N, N-di-20 acetic acid in a concentration of 16% by weight (corresponding to a yield of 63%, calculated on step d) of compound II) with a total solids content of 30% by weight and having a pH of 12.5.

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Claims (2)

A process for the preparation of trisodium salt of isoserin-N, N-diacetic acid of the formula I NaOOC-CH, OH \ I 2 -CH 2 -CH-COONa (I) NaOOC-CH 2 glycidic acid amide of formula II / ° IIO 2 / H 2c-CH-C-NH The NH (III) NaOOC-CH 2 · V * a) acrylonitrile and aqueous hydrogen peroxide are reacted with each other at a pH of 7 - 8 and at a temperature of 30 ° - 60 eC; b) unreacted acrylonitrile is distilled off; the reaction mixture is passed over a solid contact element for degradation of hydrogen peroxide; d) reacting the thus obtained aqueous solution of compound II is reacted with compound III at a pH of 7 to 9 and at a temperature of 40 ° E) the resulting solution is reacted with a basic sodium compound at a pH of 9-14 and at a temperature of 60 ° - 95 ° C; f) the resulting ammonia is removed to distil and g) the aqueous solution thus obtained is obtained from the compound I, if desired, into the solid compound I ρέ per se known per se. 2. A process according to claim 1, characterized in that the reaction steps a), d) and e) are carried out with a cascade of mixers, with at least two mixers required for each of these three steps. • · • · · · · · · · · · · · · · · · · ♦ · · · · 1 · · · · · · · ··· • · 1 <t <«